This invention generally relates to testing and burning in semiconductor components. More particularly, it relates to apparatus for controlling the temperature of high power electronic components during test or burn-in. Even more particularly, it relates to apparatus that can burn-in components dissipating substantially different amounts of power while providing each component at the same temperature.
Electronic components are operated at high temperature and voltage conditions during burn-in to weed out defective components and to establish increased reliability for those that pass. To provide the high temperature, components have been mounted in sockets on boards and the boards loaded with components mounted in forced air convection ovens. The ovens themselves are designed to provide a reasonably uniform temperature profile in all portions of the oven. When burning in relatively low power parts the oven temperature is set to approximately equal the desired burn in temperature. Higher power parts are usually burned in by decreasing the oven temperature so that self heating of the components brings them back up to the desired burn in temperature. The amount of self heating that a component experiences during burn in can be calculated by multiplying the part power (watts) by the device to air thermal resistance of the socket (degrees C per watt).
However, when high power dissipating components are operated in a low temperature oven, the variation in dissipation among the components causes substantial variation in the temperature actually experienced by the different components in the oven. Thus, the different components experience different burn-in stress temperatures depending on the heat each component and its neighbors dissipate. Also, parts have been found to vary in temperature as a result of unavoidable variation in airflow velocity and temperature in the oven.
Various systems attempting to burn-in high power components at a more uniform temperature have been disclosed. Tower systems, in which components are individually heated while nearby supporting electronics operates at low temperature, have suffered from high thermal resistance and low throughput. Liquid cooled systems have advantageously low thermal resistance, and can therefore dissipate large amounts of heat. They also have nearby control electronics that operates at low temperature. However, liquid cooled systems suffer greatly from very high cost and low throughput as compared to standard forced air convection oven systems. Thus, a better solution is needed that provides a system in which the temperature of each module can be precisely controlled without adding substantially to cost and without reducing throughput, and this solution is provided by the following invention.
It is therefore an object of the present invention to provide apparatus for burning-in large numbers of high power modules while precisely measuring and controlling the temperature of each module.
It is a further object of the present invention that the apparatus can be adapted to conventional forced air convection ovens so as to extend the usefulness of conventional ovens to high power components.
It is a further object of the present invention that the heat sink assembly can be used to control the temperature of an individual component during module test or during burn-in.
It is a feature of the present invention that apparatus includes a heat sink for temporary contact with the electronic component during burn-in, a sensor in direct contact with the electronic component and isolated from the heat sink, and a heat transferring device having input from the sensor for providing or removing heat to obtain a predetermined temperature for the component.
It is a feature of the present invention that the component to air thermal resistance through the heat sink is exceptionally low, allowing for burn in of high power parts at relatively high air temperature.
It is a feature of one embodiment of the present invention that the heat transferring device is an electrical resistance heater in direct contact with the heat sink.
It is a feature of another embodiment of the present invention that the heat transferring device comprises a cooling device.
It is a feature of this embodiment of the present invention that the cooling device for each heat sink is a fan directing air flow on that heat sink.
It is an advantage of the present invention components operate at the same temperature independent of variation in dissipation, airflow velocity and airflow temperature.
These and other objects, features, and advantages of the invention are accomplished by providing an apparatus for burning-in a plurality of electronic components dissipating high power. The apparatus comprises a chamber having a chamber temperature controller and a plurality of assemblies for burning-in components in the chamber. Each assembly comprises a socket for temporarily holding one of the components during burn-in; a heat sink for pressing in temporary direct contact with the component in the socket; a temperature sensor for sensing temperature of the component in the socket; and a heat transferring device positioned to transfer heat to or from the heat sink.
The temperature controller is a heating device, such as an electric heater or a cooling device, such as a fan. It can also be a thermoelectric device or an air or liquid impingement device. The ambient temperature in the oven is established so that the individual temperature controllers for each component can bring all components to the same specified temperature.